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如何在 C++ 中异步读取 ifstream？

[英]How do you read from a ifstream asynchronously in C++?

原文 2020-05-05 12:16:00 8 1 c++/ asynchronous/ stream/ pipe

The ifstream is reading from a UNIX pipe, currently the communication is done by sending a signal to the reading application, but I would like to get rid of the signals and use proper async io. ifstream 正在从 UNIX pipe 读取，目前通信是通过向读取应用程序发送信号来完成的，但我想摆脱信号并使用正确的异步 ZF98ED07A4D5F50F47DE1410D905FZF。

In C I would use the select() function with a timeout, so I could react immediately when there is something to read, and waith for IO otherwise.在 C 中，我会使用 select() function 超时，所以当有要读取的内容时我可以立即做出反应，否则等待 IO。

In C++ I can't access the fd of the file, so I can't use select().在 C++ 中无法访问文件的 fd，因此无法使用 select()。 What's the most reasonable approach to doing this?这样做最合理的方法是什么？ Do I have to use some sort of Boost library, or can this be done using the standard C++ libraries?我必须使用某种 Boost 库，还是可以使用标准 C++ 库来完成？

1 个解决方案

std::ifstream does not support asynchronous operations, it is designed for synchronous IO. std::ifstream不支持异步操作，它是为同步 IO 设计的。 You could build async IO around it using additional threads and IO queue, but in general this is not a good idea for efficiency reasons.您可以使用额外的线程和 IO 队列围绕它构建异步 IO，但总的来说，出于效率原因，这不是一个好主意。

For asynchronous IO you might want to look at Boost.ASIO , in particular its stream_descriptor , which can be used to adopt arbitrary stream file descriptors like pipes.对于异步 IO 您可能需要查看Boost.ASIO ，尤其是它的stream_descriptor ，它可用于采用任意 stream 文件描述符，如管道。